"Caffeine may attenuate force sensation during repeated isometric contractions and in so doing may contribute to the drug's well known ergogenic effect." (p. S59) Caffeine was administered orally (6mg/kg) and one hour later, isometric force production characteristics were measured. Ss were recorded under both caffeine and no-caffeine conditions.

It was found that force sensation was extended in the first 20 seconds of contraction but in the latter stages there was no effect. It was hypothesized that the drug affected the neural component of force production.

Implication. Caffeine causes increased force production in the early stages of an isometric contraction.